Parallel rule



1938. .1. H. BALL PARALLEL RULE Filed April 29, 19517 BY M Arrozuev Patented May 3, 1938 UNITED STATES PATENT OFFIE PARALLEL RULE John H. Ball, St. Louis, Mo.

Application April 29, 1937, Serial No. 139,653

1 Claim.

My invention relates to improvements in parallel rulers.

The main object of my invention is to provide a ruler by means of Which accurate parallel lines may be readily drawn by bookkeepers and others.

Another object is to provide a ruler of this i kind in which the operating elements are all enclosed except for the thumb wheel which is exposed and may be conveniently engaged by the users thumb to move the rule blade inward or outward as required.

Another object is to provide a ruler comprising an elongated and fiat housing having an elongated slot or recess opening out through its forward edge, a rule blade slidably mounted within the slot and held in place therein by toggle links, a thumb wheel exposed through the rear edge of the housing, and links eccentrically con necting the thumb wheel and toggle links in such manner that rotation of the thumb wheel will operate to move the rule blade straightly into or out of the housing.

With these and other objects in View the invention resides in the novel construction .and arrangement of parts as hereinafter fully set forth and claimed, reference being had to the accompanying drawing as showing a preferred embodiment of my invention for purposes of exemplification.

In the drawing:

Figure 1 is a perspective view of the ruler.

Figure 2 is a view with the housing cover removed.

Figures 3 and 4 are enlarged cross sections along the lines 3-3 and 44 respectively in Figure 2.

In carrying out my invention I provide a housing, body or rule back 5 of elongated narrow form of a length equal to the desired length of the finished rule and made of any suitable material such as metal, wood, cardboard, Celluloid or the like. This housing, as it will hereinafter be termed, has a recess or chamber 6 opening at the upper face of the rule and enclosed at the ends 1 and the lower edge 8 by uncut portions of the housing. The recess thus opens only at the upper edge 9 of the housing.

A cover or cover plate ID of the same shape and size as the housing 5 is secured by screws or rivets ll over the housing covering the face through which the recess 6 opens and the recess thus takes the form of a narrow and deep slot. An elongated flat rule blade I2 is slidably mounted edgewise down into the recess 6 through its open edge and is of such length and thickness as to just nicely slide into or out of the recess. Adjacent each end of the rule blade I2 and at aligned points in the closed bottom 8 of the recess steps I3 are cut out and in each pair of steps the ends of similarly turned or disposed 5 toggle levers or links M are pivotally connected by small pins 55 so that the levers hold the rule blade in place but by breaking at their center pivots, joints or knees it allow the blade to move in or out as desired. 10

The lower edge 8 of the housing has a slot I1 cut through at its center flush with the recess 6 and a thumb wheel I8 is journaled on a screw It in this slot ll so that the wheel extends both into the recess and out below the lower edge of the housing. Draw bars or links 23 are pivoted at their inner ends at to this wheel [8 at an eccentric point on the portion of the wheel within the recess and at their outer ends these bars are pivotally connected to the center joints l6 of the toggle levers M. The lower edge of the housing is notched out arcuately at 2| to expose as much of the knurled periphery 22 of the thumb wheel l8 as possible.

In operation with the parts in the position 25 shown the user may draw a line along the exposed edge of the blade l2 and then by turning the thumb wheel 18 in the direction indicated the toggle levers M will be operated by the draw bars 23 to draw the blade l2 downwardly or inwardly and another line may be drawn at any spacing from the first. The action of the toggle levers being the same at each end of the blade I2 the lines drawn will be parallel and any number of lines may be so drawn by moving the thumb wheel 58 as may be required. This action may be readily carried out without removing the ruler from the paper. Inasmuch as the toggle links are both turned to the same side as shown in the drawing, the resulting action is that the rule blade is moved straightly in and out of the slot or recess, thereby avoiding any danger of binding of the ends of the blade against the ends of the rule back. An important feature too is the spacing of the drawing edge of the blade I2 from the paper by the thickness of the housing 5 below the blade as indicated at 23 in Figure 3.

The ruler may of course be made in any length and size and may be graduated in inches or other dimensions if desired.

While I have herein set forth a certain preferred embodiment of my invention it is understood that I may Vary from the same in minor structural details so as best to provide a practi- 56 cal device for the purposes intended, not departing from the spirit of the invention and within. the scope of the appended claim.

I claim:

A device of the kind described, comprising a rule back recessed at its upper face and out through the predetermined forward edge, and being closed at bottom, ends and back edge, the latter however having a thumb wheel aperture formed medially therethrough, a cover plate secured over the open upper face of the rule back, thereby providing an elongated covered slot between rule back and cover plate, an elongated fiat rule blade seated edgewise and freely within the said slot, similarly turned toggle links pivotally mounted at their ends transversely within opposite ends of the said slot back of the rule blade, a thumb wheel journaled medially within the slot back of the rule blade, the periphery of the wheel being exposed through the thumb wheel slot of the rule back, and a pair of links pivotally connected at their inner ends to an eccentric point on the thumb wheel, the outer ends of the links being pivotally connected to the center joints of the toggle links.

JOHN H. BALL. 

